JPH09168166A - Circuit device for processing color under signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a device to conduct frequency conversion and filter processing with a smaller storage capacity and to be immune to the effect due to fluctuation in a color carrier frequency. SOLUTION: A color under signal modulated by a 1st carrier frequency is fed to a 1st mixer 1, in which the color under signal is converted into a 2nd carrier frequency higher than the 1st carrier frequency and an output signal of the 1st mixer 1 is fed to comb-line filter circuits 2, 3, 4, which suppress crosstalk color signals from adjacent tracks of reproduced color signals and an output signal from the comb-line filter circuits 2, 3, 4 is fed to a 2nd mixer 5, which converts the output signal of the comb-line filter circuits 2, 3, 4 into a 3rd frequency higher than the 2nd carrier frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit device for processing a color under signal reproduced by a video recorder and modulated with a carrier having a first frequency.

[0002]

2. Description of the Prior Art According to the normal recording standard for video signals of consumer video recorders, in particular the VHS standard, the color under signal is modulated at a carrier frequency lower than the carrier frequency at which the luminance signal is modulated. . At the end of reproduction, the recorded color under signal can be converted into a higher carrier frequency formed according to the color signal standard, for example the PAL or NTSC standard. Further, in the case of a video recorder, it is common to suppress a crosstalk color signal due to adjacent tracks in a reproduced color signal. For this reason, a comb filter is used.

In a known circuit arrangement of this type, the conversion of this chromatic carrier to the nominal frequency takes place upstream of the comb filter. This known configuration has the advantage that the comb filter is present in the frequency control region of the circuit arrangement,
The comb filter is clocked at four times the chromatic carrier frequency. Since this known circuit arrangement has a higher chromatic carrier frequency than the color under signal is converted, it requires a considerable storage capacity.

[0004]

Problems to be Solved by the Invention European Patent Application Publication No. 6
In another known circuit arrangement mentioned at the outset from 31446, the comb filter is arranged in a position before the color under signal is converted to a higher carrier frequency on the basis of the circuit reference. With this configuration, the storage capacity is smaller, but the color under signal read from the tape is directly supplied to the comb filter circuit. The carrier frequency of this color under signal may fluctuate considerably. Therefore, for example, the reproduction speed may change. If such carrier frequency fluctuations occur, the processing of the color under signal, particularly the processing in the comb filter circuit, will not be performed in synchronization, and the circuits in the subsequent stages that process the converted signal will not be in harmony. As a result, a defect occurs in color reproduction.

It is an object of the present invention that, in the circuit device described at the beginning, the conversion and filtering of the color under signal can be performed with the smallest storage capacity, and the influence of the fluctuation of the color carrier frequency of the signal read from the tape is influenced. It is to provide a circuit device that is not affected by the above.

[0006]

The above object is to supply a color under signal modulated at a first carrier frequency to a first mixer, and the first mixer transmits the color under signal to the first carrier. A second carrier frequency higher than the frequency is converted, the output signal of the first mixer is supplied to a comb filter circuit, and the crosstalk color signal from the adjacent track of the color signal reproduced by this filter circuit is supplied. Suppressing and supplying the output signal of the comb filter circuit to a second mixer, the second mixer converting the output signal of the comb filter circuit to a third frequency higher than the second carrier frequency. Is achieved by a circuit arrangement for processing a color under signal.

The color under signal read from the tape and modulated with a relatively low frequency color carrier is first converted by a first mixer. This color carrier frequency is then converted to a second carrier frequency which is higher than the carrier frequency from which the color signal was read from the tape. Only the output signal of this first mixer is supplied to the comb filter circuit,
This filter circuit is used to suppress the cross tote color signal generated by the adjacent track of the color under signal read. The output signal of the comb filter circuit is the second
, And converts this comb-filtered signal into a carrier frequency formed on the basis of a color signal reproduction standard.

The conversion of the color under signal read from the tape into two different carrier frequencies twice means that the circuit arrangement of the present invention is a frequency conversion, since the comb filter circuit is connected after the first mixer. Advantageously, the comb filter circuit is placed in the controlled and controlled area. On the other hand, the comb filter circuit is not supplied with the signal converted into the color carrier frequency based on the color signal reproduction standard, but is supplied with the color signal converted into the lower frequency color carrier. Therefore, the comb filter circuit can be clocked at a lower frequency than other circuit devices. Therefore, the circuit arrangement according to the invention achieves two advantages. That is, on the other hand, the advantage that the comb filter circuit is less susceptible to the fluctuation of the carrier frequency of the color under signal read from the tape is achieved. The reason for this is that the comb filter circuit is connected in the control area. On the other hand, the memory capacity required for the comb filter circuit is considerably reduced. The reason is that the supplied color signal is modulated with a color carrier having a frequency lower than the carrier frequency of the color signal corresponding to the frequency of the comb filter circuit.

A useful embodiment according to the present invention produces a third carrier frequency which is the color carrier frequency corresponding to the color signal reference. This is a beneficial advantage. The reason for this is that such a method does not require a separate conversion of the color carrier frequency.

In the case of the PAL standard color signal, the third carrier frequency is 4.43 MHz as shown in another embodiment of the present invention.

When reproducing a PAL reference signal, as shown in another embodiment of the invention, this signal is from the tape at a carrier frequency of (40 + 1/8) times the image line period of the image signal or color under signal. Read out. in this case,
A second under-color signal is converted by the first mixer
The carrier frequency of can be 4.43 / 2 MHz. As a result, the required storage capacity of the comb filter circuit can be halved.

The operation of the first and second mixers is to mix the mixed signal with the received color under signal which is modulated with the color carrier. This mixed signal is extracted from the color carrier. As a result, variations in the color carrier frequency are properly controlled, and these variations are held for the mixed signal and supplied to the mixer so that they are maintained for the color under signal to be mixed. As a result, the comb filter circuit connected to the latter stage of the first mixer of the circuit device according to the present invention is connected within the frequency range in which the frequency is controlled.

When reproducing a mixed signal in the circuit arrangement according to the invention, a mixed signal in which a color under signal modulated at the first carrier frequency is mixed is supplied to the first mixer, and the mixed signal is supplied as a voltage. The frequency of the output signal from this voltage controlled oscillator is taken out from the controlled oscillator.
An embodiment can be adopted in which control is performed according to the signal having the third carrier frequency and the output signal of the phase comparator to which the output signal of the first mixer is supplied.

In this case, the mixed signal is supplied with the first frequency, that is, the signal having a half frequency of the carrier frequency of the color signal set based on the color signal reference and the output signal of the first mixer. Is controlled by the output signal of. The phase comparison of these two signals produces a mixed signal that is fed to the first mixer. As a result, the first
The mixer output signal does not cause variations in the color carrier frequency. These variations are accommodated by this circuit arrangement. In this way, the first comb filter circuit is located in the frequency control region and is unaffected by variations in the color carrier frequency of the color under signal read from the tape, for example occurring in a special operating mode.

Second, extracting mixed signal for first mixer
Method supplies a mixed signal to the first mixer in which a color under signal modulated at the first carrier frequency is mixed, extracts the mixed signal from a voltage controlled oscillator, and outputs the mixed signal from the voltage controlled oscillator. This is achieved by controlling the frequency of the output signal in response to the signal having the third carrier frequency and the output signal of the phase comparator to which the output signal of the second mixer is supplied.

The second method has the same circuit configuration except that the signal having the carrier frequency set in the phase comparator and the output signal of the second mixer are supplied. In essence, there is no substantial difference compared to the first method of deriving the mixed signal for the first mixer.

Hereinafter, the present invention will be described in detail with reference to the drawings.

[0018]

FIG. 1 shows, as a circuit diagram, a first embodiment of a circuit arrangement according to the invention for processing a signal reproduced by a video recorder and modulated on a carrier having a first carrier frequency. This circuit arrangement has a first mixer 1 at its input. The mixer is supplied with a color under signal read from the tape and modulated at a first carrier frequency.

The output signal of the first mixer is supplied to a comb filter circuit including a first delay circuit 2, a second delay circuit 3 and an adder 4.

The output signal of the first mixer is supplied to the two delay circuits 2 and 3. These output signals are additively superposed in the adder 4.

The first delay circuit 2 has a delay OH, and
The delay circuit 3 has a delay 2H. In this regard, H
Indicates a time period of one image line of a reproduced image signal or a color signal included in the image signal. In the embodiment shown in FIG. 1, the color signal is an image signal based on the PAL standard. In this case, since the output signals of the two delay circuits are superposed, the crosstalk color signal generated by the adjacent track in the read actual color signal is suppressed. The reason for this is that the undelayed color signal and the color signal delayed over the period of two scan lines are added together.

The first delay circuit 2 has only a very simple delay, but the color under signal supplied to it is supplied to a storage element of the same type as the second delay circuit 3.
This allows the first, which does not delay the color signal by itself.
The color signal of the delay circuit 2 is subjected to the same amplitude response, that is, the same signal distortion as the signal supplied to the second delay circuit 3 which is delayed for a period of two image lines.

The output signal of the comb filter circuit, that is, the output signal of the adder 4 is supplied to the second mixer 5. The output signal forms the output signal of the circuit device and is labeled C in the drawing.
It is displayed as "Hroma Out". First mixer and second
The mixers are supplied with mixing signals for mixing operations. These mixed signals are formed by the circuit device described later.

The circuit arrangement comprises a crystal clocked oscillator 6. The oscillator produces at its output a signal having a frequency corresponding to the color carrier frequency, which signal color carrier frequency corresponds to the reproduction reference of the read color signal. This carrier wave frequency is not the color carrier wave frequency of the read signal, but is the color carrier wave frequency at which a subsequent device, for example, a television can process the color signal. For example, for a signal based on the PAL standard, this frequency is 4.43 MHz.

The output signal of this oscillator is supplied to the multiplier 7 and this signal is multiplied by 2. The output signal of the multiplier 7 is supplied to the first delay circuit and the second delay circuit 3 of the comb filter circuit so as to take the timing of the comb filter circuit.

Further, the output signal of the oscillator 6 is also supplied to a division circuit 8 which divides by 2. The output signal of this division circuit forms the mixed signal of the second mixer 5. In the second mixer 5, this mixed signal is mixed with the second input signal which is the output signal of the comb filter circuit, that is, the adder 4.

Further, the output signal of the oscillator 6 is the phase comparator 9
Also supply. The output signal of the second mixer 5 is also supplied to this phase comparator. The phase comparator 9 generates a phase comparison signal from the two supplied signals to generate a voltage controlled oscillator 1
Supply 0. The voltage controlled oscillator 10 generates an output signal having a frequency corresponding to the voltage in the phase comparison signal supplied from the phase comparator.

The output signal of the voltage controlled oscillator 10 feeds a divider 10 which divides this signal by four. The output signal of this divider forms the mixing signal for the first mixer, where it is mixed with the input signal Chroma In to which it is fed.

The color under signal read from the tape and modulated at the first color carrier frequency and supplied to the first mixer 1 is converted to the second carrier frequency. The embodiment shown in FIG. 1 is about half the color carrier frequency based on the color signal standard. The color carrier frequency set on the basis of the color signal reference will be hereinafter referred to as a reference frequency F _sc . The voltage controlled oscillator 10 has an output frequency of 4
It operates when there is no phase difference at (1/2 Fsc + 40 1/8 F _H ), and therefore when the zero voltage signal of the phase comparator exists. The color carrier frequency of the color under signal read from the tape, that is, Chroma In in the drawing is (401/8)
Become F _H. Here, F _H represents the horizontal frequency of the image signal, that is, the color under signal, and thus the line carrier frequency of these signals and the color carrier frequency F _SC set based on the transmission standard of the color signal.

The quotient of the frequency of the voltage controlled oscillator and the output signal of the divider 11 is such that the circuit carrier frequency becomes a frequency 1/2 F _SC together with the mixed signal of the output signal and the color under signal supplied to the input terminal of the circuit device. Convert. The circuit signal converted to the carrier frequency is supplied to the comb filter circuit.

As a result, the frequency of the color carrier of this signal according to the illustrated embodiment is half the frequency of the color carrier according to the reproduction standard of the color signal. This allows
The two memories 2 and 3 of the comb filter color will be timed only at the frequency 2F _SC . The memory capacities of the memory circuits 2 and 3 are halved as compared with the conventional circuit device which is timed at the frequency 4F _SC .

The output signal of the comb filter circuit is the mixer 5
At the third carrier frequency. In the circuit arrangement shown in FIG. 1, this third frequency is the _FSC and thus the color carrier frequency generated on the basis of the circuit signal reference. For the PAL standard, this frequency is 4.43 MHz. Therefore, the second mixer 5 produces at its output a color signal which can be processed by a reproduction device, for example a television.

Not only does this circuit device have a smaller memory capacity, but the comb filter circuit operates in the frequency control region of the circuit device and the frequency or phase of the circuit carrier of the color under signal supplied to its input is reduced. It has the advantage that it is not affected by fluctuations. This performance is obtained by the phase comparator performing a phase comparison between the frequency of the crystal oscillator and the circuit oscillator frequency of the output signal of the second mixer. If color variations in the color oscillator frequency of the input signal occur, these phase or frequency variations also occur in the signal of the second mixer 5. The phase comparator 9 supplies each correction signal to the voltage controlled oscillator 10 and thus the voltage controlled oscillator 10
Is adjusted to the output signal of the first mixer and the output signal of the second mixer will also have the set frequency. In this way, the frequency and phase variation of the color oscillator frequency of the input signal will be adjusted. To this end, comb filter colors or memories 2 and 3 are used.
Is supplied with a color signal modulated with a color carrier frequency of substantially constant frequency. Thus, this filter color exhibits optimum performance.

FIG. 2 shows a second embodiment of the circuit arrangement according to the invention. This circuit arrangement has the circuit elements 1 to 11 connected in the same way as the embodiment shown in FIG. 1 except for the phase comparator 9.

The circuit device shown in FIG. 2 has, instead of the phase comparator 9, a phase comparator 19 which operates in the same manner as the phase comparator 9 of the circuit device shown in FIG. On the other hand, the phase comparator 19 shown in FIG. 2 differs in its connection. The output signal of the divider 8 is supplied to the phase comparator 19 shown in FIG. Furthermore, the output signal of the first mixer is also supplied. Therefore, the phase comparator 19 in FIG. 2 compares the phase positions of the output signal of the divider 8 and the output signal of the first mixer 1.

The circuit arrangement shown in FIG. 2 as a whole is similar to that of FIG. 1 except that the voltage controlled oscillator receives from the phase comparator a correction signal which is generated in response to the phase difference between these two signals.
It operates similarly to the circuit device shown in FIG. The basic operation of this circuit arrangement has not changed at all. In the design of the circuit arrangement shown in FIGS. 1 and 2, only the different absolute phase positions of the output signals of the first and second mixers are taken into account, which absolute phase position is derived from the comb filter circuit or the two mixers. Each occurs. In these two circuit devices, the phase or frequency variation of the color carrier frequency of the color under signal read from the tape is such that the comb filter circuit is located within the frequency control region, that is, the comb filter circuit is constant. Will be adjusted to provide a color under signal modulated at the circuit carrier frequency.

[Brief description of the drawings]

1 a first circuit arrangement according to the invention for generating a mixed signal for a first mixer using the output signal of a second mixer, FIG.
It is a circuit diagram showing an example.

2 a second circuit arrangement according to the invention for generating a mixed signal for a first mixer using the output signal of a second mixer, FIG.
It is a circuit diagram showing an example.

[Explanation of symbols]

 1 1st mixer 2 1st delay circuit 3 2nd delay circuit 4 Adder 5 2nd mixer 6 Oscillator 7 Multiplier 8 Divider 9 and 19 Phase comparator 10 Voltage control oscillator

Claims (7)

[Claims] 1. A circuit device for processing a color under signal reproduced by a video recorder and modulated by a carrier of a first frequency, wherein the color under signal modulated by the first carrier frequency is a first mixer. (1), the first mixer converts the color under signal to a second carrier frequency higher than the first carrier frequency, and the output signal of the first mixer (1) is a comb filter. Circuit (2, 3, 4)
To the second mixer (5) to suppress the crosstalk color signal from the adjacent track of the color signal reproduced by the filter circuit, and to output the output signal of the comb filter circuit (2, 3, 4). And a second mixer for converting the output signal of the comb filter circuit into a third frequency higher than the second carrier frequency, thereby processing a color under signal. 2. The circuit device, wherein the third carrier frequency is a color carrier frequency formed based on a color signal reference. 3. The circuit device for processing a PAL color signal according to claim 2, wherein the third carrier frequency is 4.43 MHz. 4. A circuit arrangement according to any one of claims 1 to 3 for processing a PAL color signal, wherein the first carrier frequency is (40 + 1/8) times the image line period of the color under signal. And the second carrier frequency is 4.43 / 2 MHz. 5. The circuit arrangement according to claim 1, wherein the color mixer signal mixed with the first carrier frequency is mixed in the first mixer (1). The mixed signal is supplied, the mixed signal is extracted from the voltage controlled oscillator (10), and the frequency of the output signal from the voltage controlled oscillator is the signal having the third carrier frequency and the output of the first mixer (1). A circuit device characterized by controlling according to an output signal of a phase comparator (9) to which a signal is supplied. 6. The circuit arrangement according to claim 1, wherein the first mixer (1) is mixed with a color under signal modulated at the first carrier frequency. A mixed signal is supplied, the mixed signal is extracted from the voltage controlled oscillator (10), and the frequency of the output signal from the voltage controlled oscillator is the signal having the third carrier frequency and the output of the second mixer (5). A circuit device characterized by controlling according to an output signal of a phase comparator (9) to which a signal is supplied. 7. The circuit arrangement according to claim 1, wherein the second mixer (5) has a first mixer (1) corresponding to a half frequency of the color carrier frequency. 2) and a fixed mixed-frequency signal taken out from a fixed oscillator (6) and a divider (8) having a frequency half that of the color carrier frequency.